For producing an accurate dental restoration it is important to have the margin of the preparation of the teeth clearly visible in a dental impression. Therefore, it is often recommended to widen the sulcus in a retraction process. This is typically done by using a retraction cord or a retraction paste before the dental impression step is conducted.
This retraction step is an additional, often time consuming and sometimes difficult step to perform for the dental practitioner.
A good retraction material has the ability to keep the sulcus of a tooth open and withstand the forces of the surrounding soft dental tissue. In this respect, often pastes having a high viscosity are suggested.
However, a material having a high viscosity is not suitable as dental impression material, as this material is typically not able to reproduce the fine contours (precision) on the teeth surface, a property needed for producing an accurate dental restoration.
Technical solutions known today typically require separate pastes or materials for conducting either the dental retraction or dental impressioning process. Known are compositions which increase the viscosity upon mixture by combining two setting mechanisms.
US 2005/239958 A1 (Bublewitz et al.) describes a two-step curable mixer-suitable material for making dental impressions. The system contains at least one compound having at least two alkenyl groups, at least one organohydrogenpolysiloxane, at least one hydrosilylation catalyst, wherein at least one polymeric compound having at least one alkynyl group, at least one compound having at least one Si—OR structural unit and at least one condensation catalyst is contained.
WO 2005/013925 A1 (3M) relates to an automixable putty impression material. The composition comprises at least one polydiorganoxiloxane having at least two aliphatically unsaturated groups, at least one organohydrogenpolysiloxane, at least one alkylsiloxane having at least one carbinol, carboxy or amino group, at least one condensation cure compound and at least one addition cure precious metal catalyst.
US 2008/0200584 A1 (Bottcher et al.) describes a silicone impression material with two-stage curing mechanism. The impression material comprises at least one compound (a) with at least two alkenyl groups, at least one compound (b) with at least one chelating group, at least one organohydropolysiloxane (c), at least one hydrosilylation catalyst (d) and at least one compound with a chelatable metal component (e), the chelating group exhibiting no reactive groups which can react with component (c) and/or component (d).
EP 1 776 080 B1 (Dentsply) is directed to a method of taking a dental impression of a dentition including sub-gingival parts, comprising the steps of (i) conditioning the dentition including sub-gingival parts by application thereto of a wetting agent comprising a surfactant and a carrier; (ii) contacting the dentition with a dental impression material selected from hydrophilic and hydrophobic dental impression materials, whereby the impression material is allowed to flow into sub-gingival parts, further comprising the step of preparing the dentition with a gingival retraction cord, wherein said gingival retraction cord has been contacted with a wetting agent further comprising a hemostatic agent. Known are also references dealing with dental retraction pastes.
US 2014/0170596 A1 (Angeletakis) describes a two part retraction system than be inserted into the sulcus to form a semi-rigid porous elastomer releasing a hemostatic agent suitable for sulcus retraction such that a dental impression may be completed by a dental practitioner.
US 2010/0035213 A1 (Lubbers et al.) describes a dental kit and method for retracting sulcus. The method comprises the steps of (i) molding a dental impression of a portion of the patients mouth with a curable composition, (ii) removing the cured mold, (iii) applying an expanding silicone material with expands during curing to the adjacent area between the tooth and gingiva and (iv) reapplying the mold to the mouth of the patient to form a barrier to the expansion of the silicone material to limit the expansion of the silicon only in the direction toward the sulcus. None of the solutions described in the prior art is satisfactory.